Researchers have managed to use stem cells to regenerate the outer layer of the heart – the epicardium. The interdisciplinary team of researchers based at Pennyslavia State University, United States, say this breakthrough will bring them closer to regenerating an entire heart wall.

The research could be a major step forward in treating patients who have had heart attacks.According to the United States Centers for Disease Control and Prevention (CDC), someone in the US has a heart attack every 43 seconds.

They found that the epicardium cells they had made were similar to epicardium cells in living humans and those grown in the laboratory.The research, published in the journal Nature Biomedical Engineering, used a chemical pathway, called the Wnt signaling pathway, to regenerate the cells.

What are stem cells? Stem cells are a basic type of cell that can change into another type of more specialized cell through a process known as differentiation.Think of stem cells as a fresh ball of clay that can be shaped and morphed into any cell in the body. They grow in embryos as embryonic stem cells, used to help the rapidly growing baby form the millions of different cell types it needs to grow before birth.

In adults they are used as repair cells, used to replace those we lose through damage or ageing. Stem cells have been the focus of lots of medical research in recent decades because they can be used to grow almost any type of cell.

Dr. Xiaojun Lance Lian, assistant professor of biomedical engineering and biology, who is leading the study at Penn State, said: “In 2012, we discovered that if we treated human stem cells with chemicals that sequentially activate and inhibit Wnt signaling pathway, they become myocardium muscle cell.” In 2012, the research team managed to regenerate the Myocardium – the middle of the heart’s three layers – which is muscular and contracts, causing the heart to beat.

After their 2012 achievement, they applied the knowledge they’d gained to try to solve the puzzle of regenerating the outer layer of the heart. We needed to provide the cardiac progenitor cells with additional information in order for them to generate into epicardium cells, but prior to this study, we didn’t know what that information was,” said Lian.

“Now, we know that if we activate the cells’ Wnt signaling pathway again, we can re-drive these cardiac progenitor cells to become epicardium cells, instead of myocardium cells.”

During their study, the researchers engineered the human stem cells to become ‘reporter cells,’ meaning they expressed a fluorescent protein only when they became epicardium cells, causing the cells to glow brightly so the researchers could be certain once they’d achieved their goal.

The research could have applications in treating people with heart conditions. “Heart attacks occur due to blockage of blood vessels,” said Lian.“This blockage stops nutrients and oxygen from reaching the heart muscle, and muscle cells die.

“These muscle cells cannot regenerate themselves, so there is permanent damage, which can cause additional problems. These epicardium cells could be transplanted to the patient and potentially repair the damaged region.”

But the researchers say they still need to do more. “The last piece is turning cardiac progenitor cells to endocardium cells (the heart’s inner layer), and we are making progress on that,” said Lian.

This isn’t the first time heart tissue has been grown in a lab. In 2015 researchers generated a working heart from skin cells that were turned into stem cells.The team of researchers at Massachusetts General Hospital and Harvard Medical School stripped off cells from donor hearts and infused the hearts with a solution of the stem cells and nutrients to allow them to grow on the structure of the donor heart.

In another 2015 study, researchers at the University of California, Berkeley, in collaboration with scientists at the Gladstone Institutes used stem cells to create tiny, beating hearts with the hopes of using them to test new drugs.